1. Field of the Invention
The present invention relates generally to a digital audio data accumulation device. More specifically, the invention relates to a digital audio data accumulation device for recording and reproducing a digital audio data in and from an audio data storage system having a faulty storage portion.
2. Description of the Related Art
Conventionally, in order to accumulate digital audio data in a digital audio data accumulation device, there is a system which records and reproduce audio data in and from an audio data storage system having a sequence of normal storage portions from a leading address while avoiding a faulty storage portion, as illustrated in FIG. 16.
This method restricts in the audio storage device by requiring of sequential normal storage region from the leading address. In this method, the audio data is stored in the storage region subsequent to the sequential normal storage region from the leading address and up to the trailing end. Recording of the audio data can be performed even when a faulty storage region is present in the storage region for the audio data.
In the accumulating method of the digital audio data as set forth above, the audio storage region including the faulty storage region is divided into equal size sub-regions for managing each sub-regions individually. Namely, in the sequence of normal storage region from the known leading address (address 0) (storage region from address 0 to address n: segment table), a faulty address table is generated.
In such audio recording device, the audio storage region [storage region of address (n+1) and subsequent storage region] including faulty storage portion [storage region of address (n+201) to address (n+300)] is divided into n in number of sub-regions to be managed per sub-region. With respect to each of the divided sub-regions, faulty inspection is performed. The result of faulty inspection is stored in the faulty address table. It should be noted that the sub-regions which can be used and the sub-regions which cannot be used are determined depending upon presence or absence of the faulty bit in the audio storage device.
The faulty sub-region has significant influence particularly for compressed audio coded data. In the extreme case, it is heard as noise. Therefore, by setting an error flag (ERROR FLAG), the use of the faulty sub-region is prohibited.
For example, since segment region 1 from address (n+1) to address (n+100) can be used, the error flag of the segment 1 in the segment table is set to OFF. Also, since the segment region 2 from address (n+101) to address (n+200) can be used, the error flag of the segment 2 in the segment table is also set OFF.
In contrast to this, since the segment region 3 from address (n+201) to address (n+300) cannot be used, the error flag of the segment 3 in the segment table is set to ON.
When the audio data is stored in the audio storage device, or when the audio data is read out from the audio storage device, reference is made to the faulty address table corresponding to the respective of the abovementioned sub-regions so that storing and reading out for the audio storage device is performed according to the result of the reference made.
As the device for accumulating audio data, in the consumer field which is a particularly large market, the audio accumulation device employing a tape as a storage medium is built in an automatic-answering and recording telephone, or a voice memo device, and so forth.
However, in the frequently used application, such as in the consumer field, a problem may arise in maintenance or durability of the data audio recording apparatus, or in operability (response speed and so forth).
Therefore, the digital audio data accumulation device utilizing audio data compressing and decompressing technology implemented in a semiconductor chip is becoming a built-in device in the equipments in the consumer field. In particular, with the tendency of decreasing of cost per bit of the audio storage device of the semiconductor chip, it is becoming possible to realize low cost of the digital audio data accumulation device.
In such case, application of the audio storage device having certain amount of faulty storage portion in the audio data storage system by commercialization thereof, significantly contributes to the lowering of cost per bit of the audio storage device. The semiconductor audio storage device including faulty storage portion is normally the faulty product in the semiconductor fabricating process to be disposed. By application of such semiconductor audio storage device including faulty storage portion to the audio storage device, a cost for disposing of such faulty product becomes zero and, more beneficially, by commercialization of such faulty products, the cost becomes approximately half to one third of the normal audio storage device having no faulty storage portion.
In the conventional digital audio data accumulation device as set forth above, there is a constraint to have sequence of normal region from the leading address to limit number of audio storage devices of the faulty semiconductor products to pass preliminary inspection. Such limitation of number of the faulty semiconductor products to be used as the audio storage device should cause a problem in supply amount as consumer use product.